A major problem exists with diagnosis at the behavioral level because behavioral features may appear together by chance e.g. a child may be tall, colour blind and red haired. So how was the clustering together of three impairments a part of a syndrome (a pattern of symptoms that cluster together)?

The fundamental work that answered this question was done by Lorna Wing and Judith Gould in 1979. They carried out an epidemiological survey of all children living in an area of South London called Camberwell.

From the total population of children under 15 (35,000) all children known to the social, educational and health services (914) were screened. Children were selected from the group if they had severe learning difficulties, and/or if they showed one of the following:

Social impairment;

Verbal and non-verbal language impairment; and

Repetitive/stereotyped activities.

The screening resulted in a group of 132 children whom attended special schools, and who ranged from 2 to 18 years. The children were observed and given medical and psychological tests and their carers interviewed using a schedule devised by the researchers.

The group was divided on the basis of social behaviour into 58 children with appropriate social interaction and 74 socially impaired subjects. The groups did not differ in age but more males were seen in the socially impaired group.

Further analysis led the researchers to conclude:

'all the children with social impairments had repetitive stereotyped behaviour and almost all had absence or abnormalities of language and symbolic activities. Thus the study showed a marked tendency for these problems to occur together'.

The pioneering work of Lorna Wing gave rise to the concept of the triad of impairments. What follows is a brief look at the typical behavioral traits seen in each of the three impairments:

Kanner highlighted the delay or absence of speech in his diagnosis. Use of speech varies from not at all (in 20% of cases) to a very good level of language. Common speech problems include:

Repeating words spoken to them (echolalia);

Asking for things by repeating a phrase they associate with the action e.g. 'Do you want a cup of tea' instead of 'I want a cup of tea';

Missing linking words out of sentences such as 'in' 'on' 'because' 'under.' So, for example a child may say 'go car shop' missing out the joining words;

Explaining in greater detail than is necessary;

Long replies to questions spoken as if learnt from a book.

3.3.2 Understanding speech

So, as speech varies, so does understanding of speech. Even in the worst cases, most people with autism can understand some speech. Difficulties arise in a number of situations:

When objects have more than one name such as a bowl (washing up or eating from?);

Confusion between the sound of a word e.g. meet and meat;

Literal interpretation can be problematic. Imagine if you took phrases like 'it's raining cats and dogs' or 'have you lost your tongue' literally;

Humour, especially that which relates to verbal ambiguity can be difficult for a person with autism.

3.3.3 Intonation and voice control

There are a number of characteristics that relate to the way speech is made which can be found in a person with autism. These include:

Problems with volume � sometimes too loud; often too quiet;

The voice may sound mechanical or monotonous;

Enunciation of words can be over-emphasised.

3.3.4 Using and understanding non-verbal communication

Speech is only one of a variety of ways in which people communicate, all sorts of gestures accompany speech including subtle eye movements, arm and hand movements and posture changes. People who are not autistic but have an impairment in, say, speech are able to use other ways of communicating. However people with autism have a fundamental impairment in communication, which goes beyond just speech.

Thus a person with autism is unlikely to develop additional communication skills and whilst some of the more severely impaired can learn some manual sign language they will never use them spontaneously.

As we have already seen, one of the characteristics of autism is the inability to play or engage in imaginative activities. So a toy truck becomes a play thing only in as much as the spinning of a wheel provides stimulation. Some more able people with autism develop a sequence of events which appear to be play but close observation shows the sequence is often repeated over and over again.

The lack of imaginative play leads on to limited or no understanding of other people's emotions so people with autism find difficulty in sharing happiness or sorrow with others.

Many people with autism find their pleasure in special interests.

3.4.1 Repetitive stereotyped activities

Many people with autism display stereotyped activities. These range from the simple such as:

Tasting, smelling, feeling or tapping different surfaces;

Listening to mechanical noises such as washing machines;

Switching lights on and off;

Spinning objects;

Head banging.

These simple stereotypies may last until adulthood. More complex stereotyped behaviors include:

A complex sequence of bodily movements;

Placing objects in long lines that cannot be moved;

Extensive bedtime routines;

The family sitting in exactly the same places at mealtimes;

Attachment to strange objects such as pieces of string or leaves;

Collecting strange objects such as tins of polish;

In more able people with autism, fascination with the weather, timetables, train numbers, etc, etc may be found.

Many of the above do not extend into adulthood. However, fascination with numbers and sequences can often continue.

3.5 Other features

Lorna Wing observes a number of additional features which in themselves are not universal and not critical for diagnosis. These include:

Stereotyped movements - such as finger flapping, arm waving, jumping, head rolling and walking on tiptoe;

Abnormalities of gait and posture are sometimes seen � where the child may not swing his/her arms properly when walking, may hold their hands out when walking or may bend their fingers or arms in unusual ways;

The person with autism may have marked difficulties with physical education and games. This is especially the case with team sports.

3.5.1 Responses to sensory stimuli

People with autism may react to sound and visual stimuli in unusual ways:

A person with autism may not react to a very loud noise but will respond to a favorite theme tune or a food being prepared;

Some children with autism can display unusual abilities to move and find objects in near darkness and some may show distress when exposed to very bright lights;

Sensitivities to smell, taste and certain textures have been noticed and some people with autism display indifference to pain;

Feeding difficulties can occur, such as the child who would only eat white coloured food.

3.5.2 Inappropriate behavior

Inappropriate, difficult behavior is frequent in children with autism. This may manifest itself in a number of ways:

Confusion and fear of unfamiliar circumstances;

Restlessness, destructive and aggressive behavior can occur;

Screaming in public can happen as can temper tantrums;

People with autism generally will not lie so if they see what they consider to be an ugly baby or a very short person they may well point this out!